As Channel 4 prepares to air an update of Hugh's Fish Fight on Monday evening, retailers have today revealed how sales of fish have changed as a direct result of the high profile campaign.

Hugh Fearnley-Whittingstall's campaign has garnered support from more than 700,000 people since the programme first aired in January, demanding the EU reform its Common Fisheries Policy in order to end the controversial practice of discarding and better protect European fish stocks.

As a result of the campaign, retailers also came under pressure to promote less fashionable fish varieties and provide clearer information to customers about the environmental impact of the fish they choose to buy.

A number of supermarkets responded with a series of initiatives designed to encourage shoppers to switch to alternative fish varieties where stocks are more healthy.

Sainsbury's has today revealed it has sold 46 extra tonnes of alternative fish varieties such as coley, pouting, rainbow trout, hake and megrim following the launch of its Switch the Fish campaign in June.

The campaign encouraged shoppers to try new species and take the pressure off the 'big five' - cod, haddock, salmon, prawns and tuna.

Waitrose said it has also seen a marked and long term change in fish sales trends since January, with demand for white fish alternatives to cod and haddock soaring.

Shoppers also took Fearnley-Whittingstall's advice to eat more mackerel, which is native to Britain and boasts a healthy population. Sales at Waitrose are up 105 per cent since January.

Similarly, Birdseye said total sales of Pollock products are up six per cent partly as a result of the Fish Fight campaign, while sales of battered and breaded XL Pollock grew by 41 per cent.

Hugh's Fish Fight: The Battle Continues, will broadcast at 9pm this evening, and will provide an update on the campaign, and emphasise the work that still needs to be done to secure future fish sources.

Despite the fact that the European Commission last month published proposals for a new Common Fisheries Policy, including recommendations for a discard ban, there is still another 18 months to go before the new policy becomes law.

The proposals have been broadly welcomed by environmental groups, but representatives of the fishing industry have warned that the plans could have a negative impact on fishermens' income.

Martin Glenn, chief executive of Birds Eye Iglo Group, hailed the changes in consumer buying habits but he also called for decision makers to boost their efforts to drive change.

"The success of [Hugh's] campaign has been directly reflected through the growing popularity of our Pollock fish fingers," he said.

"However, a lot of work still needs to be done to secure our future fish sources, which is why we are continuing to drive collaboration between the government and the wider industry to encourage better fisheries management."